Evaluation of intaglio surface trueness and margin quality of interim crowns in accordance with the build angle of stereolithography apparatus 3-dimensional printing

Abstract

Statement of problem: Studies on the intaglio surface trueness and margin quality of interim crowns fabricated using stereolithography apparatus (SLA) 3D printing depending on the type of tooth and the build angle are lacking.

Purpose: The purpose of this in vitro study was to evaluate the effects of intaglio surface trueness and margin quality in accordance with the type of tooth and the build angles of interim crowns fabricated by SLA 3D printing.

Material and methods: A definitive cast was digitized for computer-aided design (CAD) reference model (CRM) production, and the interim crown was designed by using a CAD software program and saved as a standard tessellation language (STL) file. For CAD test model (CTM) production, 3D printing was performed in accordance with the type of tooth (maxillary central incisor, first premolar, and first molar) and the build angles (90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees) (n=17). The intaglio surface of the printed interim crown was digitized. CRM and CTM used 3D inspection software to analyze the intaglio surface superimposition and root mean square (RMS). In addition, a grading system was developed to evaluate the margin quality, which was assessed visually. Statistical analysis was performed using 1-way ANOVA, 2-way ANOVA, and the Tukey honestly significant difference post hoc test (α=.05).

Results: The RMS value showed significant differences in the various types of tooth as per the build angles (P<.001). The central incisor and first premolar showed the lowest RMS value at 180 degrees, and the first molar showed the lowest RMS value at 210 degrees. The margin quality was significantly different as per the build angle in the central incisor and the first molar (P<.05). The worst margin quality observed in all teeth was at 180 degrees.

Conclusions: In 3D printing, the build angle affected the intaglio surface trueness of the interim crown. The recommended build angle for interim crowns fabricated using 3D printing is between 150 and 210 degrees. The tooth type affected the margin quality according to the build angle, except in the case of first premolars.